The invention is in the field of laser designators used in accordance with laser guided weapon delivery systems of laser countermeasure systems, and particularly relates to a technique for boresighting a laser beam to the video sensor of the laser designator system.
Modern weapon delivery systems strive to establish a high probability of first pass target destruction by attack aircraft. Performance requirements are especially acute in aircraft mounted laser designator system applications, which typically are incorporated in a pod configuration, and in such an embodiment, required system pointing accuracies are on the order of tenths of a milliradian. Automatic television tracker systems including television point trackers or area correlation trackers operating with compatible sensors such as vidicons, have been found to be capable of meeting these performancy requirements. The tracker measures the alignment error between the line of sight to the target and the optical system pointing vector and issues error signals which command the system servos to correct the system pointing vector to achieve the desired result.
For a truly effective fire control system, the laser beam to be directed at the distant target must be boresighted to the television tracker system. Prior boresighting systems include those which sighted the laser designator pod apart from the aircraft such as during initial assembly only, or at scheduled intervals in a maintenance shop. Other systems permit boresighting while the laser pod is installed on the aircraft. However, these prior art systems are limited to occasional boresighting on laser secure ranges or to flight line boresighting to each mission. The type of system which would allow for the smallest boresight error over many missions is the type which is based upon airborne boresighting. Airborne boresighting techniques may involve the alignment of the laser optical axis only once at the beginning of the mission in response to a pilot initiated command, or boresighting may be initiated each time the fire control system is activated.
Examples of known laser boresighting techniques are given in U.S. Pat. No. 3,628,868 issued Dec. 21, 1971 to Starkey and U.S. Pat. No. 3,752,587 issued Aug. 14, 1973 to Meyers et al. Starkey shows a laser boresight device which has a telescope mounted on the housing of the laser and accomplishes boresighting through manual micrometer adjustments. Meyers discloses a boresighting device which utilizes a strip of material to which the laser is directed during the boresighting operation. The laser will burn a hole through the strip allowing light to pass therethrough to the television sensor. The image thus created is aligned on the television camera through the manual adjustment of the horizontal and vertical potentiometers, which position the image with respect to optical crosshairs. Neither of these references disclose automatic boresighting, and this fact is quite significant when it is realized that the pilot is preoccupied with aircraft flight tasks, and in such circumstances cannot perform manual laser boresighting accurately and reliably.